Question

Calculate the pH of 100.00 mL of an ammonia buffer (pKb = 4.76), prepared by placing 55.0 mL of concentrated NH4OH (i.e., NH3; 14.5 M) into a volumetric flask, adding 6.76 g of ammonium chloride, and diluting to the mark with DI water.
What size flask? I will assume 100 mL volumetric flask AND I will assume adding solid NH4Cl does not change the volume.
M NH3 = 14.5 x 55 mL/100 mL = ?

mols NH4Cl = grams/molar mass = ?
M NH4Cl = mols/L

pH = pKa + log(base)/(acid)
You are given pKb.
PKa + pKb = pKw = 14

Post your work if you get stuck.

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